The unpleasantness of urine malodour is an age-old problem. When urine is excreted into absorbent articles such as clothing, diapers or incontinence pads, or onto floors surrounding urinals or WC bowls, an ammoniacal malodour may often be detected within a short time. The same problem occurs in pet litter, and may of course be relevant anywhere in the house for households including cats or dogs, etc.
Urine is a clear, transparent fluid that normally has an amber color, and when fresh is generally of low odour. The average amount of urine excreted by a human in 24 hours is about 1,200 cubic centimeters. Chemically, urine is mainly an aqueous solution of sodium chloride and organic substances such as urea and uric acid. Normally, it contains about 960 parts of water to 40 parts of solid matter. Many hundreds of different mineral salts and organic compounds are present in urine, albeit at trace levels for a significant proportion of these. The pH of normal urine is between 4.5 and 7.8, but usually it ranges between 5.0 and 6.0, due to obligatory excretion of acid produced every day.
The major components of urine malodour are: ammonia, volatile fatty acids (primarily acetic, propionic, butyric, formic); volatile sulphur compounds e.g hydrogen sulfide (H2S) and methyl sulphides such as methyl mercaptan (CH3SH); other nitrogenous compounds such as indole, skatole, pyridine, pyrrole, ethylamine; various other volatiles including benzyl alcohol, phenol, p-cresol, ethanol, methanol, acetone, methyl ethyl ketone, acetaldehyde, propionaldehyde, pentanone, heptanone, propanol, butanol, octanol. These odourous molecules are mainly produced as a result of the bacterial degradation of exogenous materials such as urea and uric acid found in urine, though trace levels of certain materials may reflect materials found in the diet or in the environment. The nitrogenous bases, in particular ammonia, contribute significantly to the malodour recognised by most people from used diapers or other hygiene products such as adult incontinence products. This malodour arises at least partly from the bacterially mediated degradation of urea, from the metabolism of microorganisms present on the skin or from the urogenital tract, for example from the growth of Proteus and Micrococcus species. All strains of Proteus spp. form the enzyme urease during their metabolism. Urease has the ability to rapidly break down urea (constituting about 2% of human urine) into ammonia causing unpleasant odour. The headspace composition above stale urine comprises a variety of materials, but the dominant malodour contributor under most conditions is invariably ammonia. Techniques that lead to reduction in the amount of ammonia present above urine are therefore of possible utility in product sectors associated with sanitation, hygiene, and incontinence. Several approaches are known in the art that address this need.
Antimicrobial agents used in personal products are designed to reduce the population, inhibit the growth or diminish the metabolic activities of microorganisms associated closely with the body—on the surface of the skin, in mucosal surfaces, in the urogenital tract, etc. Typical agents of this nature include triclosan (2′,4,4′-trichloro-2-hydroxydiphenyl ether) and zinc oxide which are well known to exert antimicrobial and deodourant effects. The use of common deodourant actives results in a non-selective antimicrobial action exerted upon most of the skin's natural microflora. This can represent an undesirable feature of such deodourant formulations, since the natural microflora provides a protective barrier (colonisation resistance) against invasion by potentially pathogenic bacteria. Certain perfume components and mixtures thereof may contribute to such antimicrobial effects. For example, published US application US2004266302 relates to a disposable absorbent article containing an encapsulated antimicrobial essential oil for odour control. PCT publication WO 2002/47472 relates to products and methods that utilise a urease inhibitor formed from a polyanionic, and preferably amine-based, chelating agent and a divalent heavy metal ion, to prevent or minimize ammonia odour produced by the degradation of urea in secreted or excreted body fluids. Similarly WO 97/46187 relates to absorbent articles in particular sanitary napkins and panty liners having an odour control system comprising a polyfunctionally substituted aromatic chelating agent for improved odour control.
Much of the art is concerned with the use of odour absorbent materials. For example, WO 2001/80915 relates to absorbent articles that comprise a cationic polysaccharide, preferably chitosan material, and silicate. These articles claim to deliver improved odour control performance (synergistic odour reduction) and improved fluid handling properties/absorption performance. WO 94/25077 relates to odour control through an absorbent article containing a boric acid/sodium tetraborate buffer. EP 509409 relates to malodour control though the design of an absorbent article containing a deodourizing blend of anhydrous, non-buffer blend of at least basic and pH neutral odour absorbing particles. U.S. Pat. No. 6,031,147 discloses an absorbent product comprising a hydrogel-forming polymeric absorbent material and a surface-active agent such as ethoxylated sorbitan monooleate, having a hydrophilic/lipophilic balance of less than about 12.
WO 99/06078 describes absorbent materials containing cyclodextrin as an odour control material. WO 98/26808 describes odour control provided by a combination of a material that inhibits the formation of odour (and has at least one attribute selected from the group consisting of antimicrobial activity, urease inhibition activity, pH adjustment activity) and an odour-absorbing material for objectionable odour molecules selected from the group consisting of cyclodextrin, zeolite, activated carbon, kieselguhr, acid salt forming materials and mixtures thereof. The scent signal is provided by cyclodextrin/perfume inclusion complexes and/or matrix perfume microcapsules to assure the wearer that the product is working.
WO 2000/51652 describes the use of oxidising agents such as a peroxyacid in combination with an odour-absorbing agent such as silica and/or zeolite. WO2003/051413 and WO 2003/051410 relate to a fibrous absorbent material or cellulose fibers treated with a carboxylic acid based odour control agent.
Perfumes have long been recognised as beneficial in hygiene and sanitary sectors. WO 98/25562 describes a diaper design that contains perfume zones and microcapsules as release agents to provide odour control. Published application US 2003/072733 describes a process for absorbing moisture and/or malodour while providing a fragrance to the surrounding ambience. WO 2005/044320 relates to a dual purpose volatile substance controlling composition comprising a sorbent and a fragrance component designed to control malodours including those resulting from bodily fluids. The design involves volatile substance sorption directly linked to fragrance release.
Perfumes may simply mask malodours. WO 2004/10325 describes sanitary absorbent articles comprising a non-aqueous volatile cooling agent such as menthyl lactate or perfume. WO 2004/108177 describes the incorporation of a starch-encapsulated accord into products that releases perfume to minimise odour. However, perfume compositions have been disclosed which exhibit effective deodourant action for specific malodours. For example, WO 2000/01356 describes certain perfume components and compositions thereof, useful in reducing or preventing body malodour. The perfume components (or compositions comprising the perfume components) are described as inhibiting coryneform bacteria that are capable of catabolising fatty acids and are responsible for the production of short chain fatty acid malodour. In this way, the perfume components (or compositions thereof) in-use produce a deodourant effect. However, many of the deodourant perfumes disclosed in the art have relatively high odour intensities that are unsuitable for use in the sanitary or incontinence product sector, and/or are not effective in counteracting or inhibiting ammonia malodour.
In spite of the above mentioned disclosures there still exists a need for cost-effective products that combat urine-derived malodour more efficiently, both from the perspective of malodour prevention as well as malodour amelioration, and do not suffer from the potential disadvantages of exploiting highly antimicrobial actives, whilst benefiting from the presence of perfumes that enjoy broad consumer acceptability.
It has now been surprisingly found that particular perfume compositions are capable of inhibiting the development of ammonia from urea at sub-minimum inhibitory growth concentrations (MIC), and are effective in counteracting urine malodour in spite of exhibiting relatively low perfume odour intensities.